A refrigerant fluid circuit of the above type is known from French patent specification FR 2 717 126A, and from the specification of French patent application no. 9611325. The refrigerant fluid is able to flow either in the air conditioning loop, with the circuit operating as a conventional air conditioning circuit, or in the heating loop, in which case the circuit is then operating as a heating circuit which gives additional heating.
In a circuit of that type, as is explained in particular in French patent specification no. 9611325, the distribution means in the heating branch comprise a stop valve of the two-way type, which is preferably an electromechanical valve. This stop valve, which operates on a "all or nothing" basis, is controlled in coordination with a further stop valve which is connected in the second branch, in such a way that they together constitute a fluid flow switching means for controlling the flow of fluid in the air conditioning loop or in the heating loop.
In this known circuit, expansion means are also provided, being connected in the heating loop downstream of the distribution means with respect to the direction of flow of the refrigerant fluid. This expansion means, which enables the flow of refrigerant fluid in the heating branch to be interrupted or restricted momentarily, is preferably made in the form of a differential pressure regulator which enables the refrigerant fluid to flow only when the pressure difference between its inlet and its outlet exceeds a predetermined threshold value.
Thus, in this known circuit, it is necessary to provide two different means so as to ensure, on the one hand, the function of distribution of the refrigerant fluid into the heating loop, and on the other hand, the function of expansion of the refrigerant fluid in the gaseous state. The known circuit thus has the disadvantage that it calls for two components to fulfil these two functions, and this adds to the size of the apparatus.
In addition, the differential pressure regulator interposed in the heating branch does not enable the quantity of refrigerant fluid flowing in the heating loop to be perfectly controlled as a function of demand.